This study explores the hysteresis phenomenon in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) monolayers, considering several variables, including temperature, compression and expansion rates, residence time, and subphase content. The investigation focuses on analyzing the influence of these variables on key indicators such as the π-A isotherm curve, loop area, and compression modulus. By employing the Langmuir–Blodgett technique, the findings reveal that all the examined factors significantly affect the aforementioned parameters. Notably, the hysteresis loop, representing dissipated energy, provides valuable insights into the monolayer’s viscoelasticity, molecular packing, phase transition changes, and resistance during the isocycle process. These findings contribute to a comprehensive understanding of the structural and dynamic properties of DPPC monolayers, offering insights into their behavior under varying conditions. Moreover, the knowledge gained from this study can aid in the development of precise models and strategies for controlling and manipulating monolayer properties, with potential applications in drug delivery systems, surface coatings, as well as further investigation into air penetration into alveoli and the blinking mechanism.

In this paper, analysis of π-A isotherm curves, oscillatory dilatational deformation, and microstructure imaging with atomic force microscopy (AFM) has revealed complex behaviors of lipid monolayers. The π-A isotherm hysteresis analysis opens a new discourse on the physical properties of lipid monolayers. Isocycle curves of lipid mixtures elucidate how changes in the molecular packing affect the dynamics of the monolayer. Notably, DPPC monolayers exhibit the lowest hysteresis energy, reflecting high mechanical reversibility during compression-expansion cycles. In contrast, the introduction of POPC (i.e., as molar fractions x_POPC = 0, 0.25, 0.5, 0.75, and 1) into the lipid mixture disrupts the tight packing and increases the hysteresis. AFM images highlight the emergence of lipid domains (LE-LC phase transition and LC phase), which complement the observations from π-A isotherms at surface pressures of 5 and 24 mN/m. Furthermore, examination of interfacial dilatational rheology through barrier oscillation provides quantitative information about monolayer deformation. Our findings reveal that the lipid mixture, surface pressure, frequency, and amplitude sweeping influence the elastic and viscoelastic behavior of the lipid monolayer. Additionally, Lissajous plots from amplitude sweeping effectively distinguish the linear and nonlinear behavior of the monolayer.

PCV2 is a significant epidemic agricultural pathogen that causes a variety of swine diseases. PCV2 infections have significant economic impact on the swine industry, making effective strategies for rapid detection of PCV2 in pigs essential. Herein, we report on the synthesis of the so-called nano-MIPs which can be utilized for molecular recognition of PCV2. The morphology and structure of nano-MIPs were characterized using scanning electron microscopy (SEM). Nano-MIPs are spherical with sizes around 120–150 nm. Binding experiments demonstrate that the fluorescence intensity of PCV2 samples decreases proportionally to increasing the concentration of nano-MIPs due to quenching, while non-imprinted polymer nanoparticles (nano-NIPs) do not affect the signal. The Stern–Volmer constant of nano-MIPs binding to PCV2 was 1.3 × 10⁻³ mL/µg, whereas nano-NIPs led to 7 × 10⁻⁵ mL/µg, i.e., 1.8 orders of magnitude lower. The detection limit for binding MIP particles to PCV2 by fluorescence measurements is 47 µg/mL. This affinity test allows for designing both direct and competitive quartz crystal microbalance (QCM) assays for PCV2 leading to QCM measurements. The QCM results show nano-MIPs binding to PCV2 immobilized on the sensor surface with appreciable reproducibility. QCM sensor characteristics reveal signal saturation above around 200 µg/mL at a response of − 354 Hz and an LOD of approximately 35 µg/mL. Nano-MIPs also show selectivity factors of 2–5 for CSFV and PRRSV probably because the three viruses have similar diameters around 50 nm. Graphical Abstract

Lipid‐based nanodelivery systems are now widely used in the pharmaceutical and food industries to enhance the delivery of bioactive compounds by leveraging the properties of lipids. Nanostructured lipid carriers (NLC), as one of the lipid‐based nano‐delivery systems, employs a blend of solid and liquid lipids, which improves the solubility, stability, and bioavailability of bioactive substances. This study aimed to optimize the NLC containing thymoquinone‐rich oil (NLC‐TQO) formulation using the Box–Behnken design; assess its antioxidant activity and oxidative stability by measuring 2,2‐diphenyl−1‐picrylhydrazyl (DPPH) radical scavenging activity, thymoquinone (TQ), and tocopherol contents over 28‐day storage; and evaluate the impact of incorporating beta‐carotene as singlet oxygen quencher on the oxidative stability of the NLC‐TQO. The optimized formulation involved 4.16% lipids (glyceryl monostearate and TQO), 5.85% Tween 80 as the surfactant, and 8.20 min of ultrasonication. NLC formulations demonstrated better DPPH activity retention than the emulsions, with cold and dark storage conditions being the most effective for preserving antioxidant activity. TQ stability in the NLC was observed at elevated temperatures without light, with around 50% remaining intact. However, TQ degraded rapidly under light, almost entirely by day 7. Gamma‐tocopherol exhibited better stability than alpha‐tocopherol, especially under light. The addition of beta‐carotene enhanced NLC‐TQO's oxidative stability. These findings revealed the potential of the NLC formulation as an effective delivery system for TQ with better oxidative protection compared to emulsions, making it a promising option for pharmaceutical and food industry applications.

This study investigated the biophysical impacts of methyl-β-cyclodextrin (MβCD) on supported lipid bilayers composed of DPPC/POPE (1:1) and DPPC/POPE/Chol (1:1:2). Using Quartz Crystal Microbalance with Dissipation (QCM-D), Atomic Force Microscopy (AFM) imaging and force–distance (F–D) curve analysis, we monitored vesicle fusion, assessed bilayer symmetry, and evaluated mechanical stability before and after MβCD treatment. The DPPC/POPE bilayer initially showed a distinct “kink” in its F–D curve and a single breakthrough force, indicating a relatively asymmetric and heterogenous structure. Upon MβCD treatment, the bilayer exhibited symmetry, as evidenced by breakthrough force profiles. Similarly, the cholesterol-containing DPPC/POPE/Chol bilayers displayed two breakthrough points, signifying distinct lipid domains, higher rigidity, and heterogeneity. After one hour of MβCD treatment, these bilayers became more homogeneous and showed a single breakthrough peak—evidence of successful cholesterol or phospholipid extraction. Breakthrough force histograms reinforced these findings by revealing substantial shifts in force distributions. Complementary dynamic light scattering (DLS) and zeta potential measurements confirmed vesicle size and surface charge, while QCM detected notable mass loss in cholesterol-rich bilayers at elevated temperatures. Collectively, these findings underscore the role of cholesterol in bilayer architecture and validate MβCD as an effective modulator of bilayer composition and symmetry.